Alpha-olefins, especially those containing 6 to 20 carbon atoms, are important items of commerce. They are used as intermediates in the manufacture of detergents, as monomers (especially in linear low-density polyethylene), and as intermediates for many other types of products. Consequently, improved methods of making these compounds are desired. Especially desired, is a process capable of making a range of linear α-olefins such as 1-butene and 1-hexene.
Most commercially produced alpha-olefins are made by the oligomerization of ethylene, catalyzed by various types of compounds, see for instance B. Elvers, et al., Ed. Ullmann's Encyclopedia of Industrial Chemistry, Vol. A13, VCH Verlagsgesellschaft mbH, Weinheim, 1989, p. 243-247 and 275-276, and B. Cornils, et al., Ed., Applied Homogeneous Catalysis with Organometallic Compounds, A Comprehensive Handbook, Vol. 1, VCH Verlagsgesellschaft mbH, Weinheim, 1996, p. 245-258. The major types of commercially used catalysts are alkylaluminum compounds, certain nickel-phosphine complexes, and a titanium halide with a Lewis acid. In all of these processes, significant amounts of branched internal olefins and diolefins are produced. Since in most instances these are undesirable and often difficult to separate, these byproducts are avoided commercially.
More recently, some iron complexes bearing tridentate chelating bis(imino)pyridine ligands have been reported, produce oligomers when activated (B. L. Small and M. Brookhart, J. Am. Chem. Soc. 1998, 120, 7143; M. Brookhart and B. L. Small, PCT Int. Appl. WO9902472, 1999 (DuPont)). Imino-bipyridine based iron complexes when activated produce low molecular weight oligomers (G. J. P. Britovsek, S. D. Baugh, O. Hoarau, V. C. Gibson, D. F. Wass, A. J. P. White, D. J. Williams, Inorg. Chim. Acta 2003, 345, 279. Bis(hydrazone)pyridine complexes of iron afford mixtures of low molecular weight polymer and oligomers (G. J. P. Britovsek, V. C. Gibson, B. S. Kimberley, S. Mastroianni, C. Redshaw, G. A. Solan, A. J. P. White, D. J. Williams, J. Chem. Soc., Dalton Trans. 2001, 1639; M. O. Kristen, A. Gonioukh, D. Lilge, S. Lehmann, B. Bildstein, C. Amort, M. Malaun PCT Int. Appl. WO0114391, 2001 (BASF); L. S. Moody, P. B. MacKenzie, C. M. Killian, G. G. Lavoie, J. A. Ponasik Jr., T. W. Smith, J. C. Pearson, A. G. M. Barrett, G. W. Coates, PCT Int. Appl. WO0183571, 2001 (Eastman); L. S. Moody, P. B. MacKenzie, C. M. Killian, G. G. Lavoie, J. A. Ponasik Jr., A. G. M. Barrett, T. W. Smith, J. C. Pearson, PCT Int. Appl. WO0050470, 2000 (Eastman)). Iron based oligomerization catalysts have been reported in G. J. P. Britovsek, S. Mastroianni, G. A. Solan, S. P. D. Baugh, C. Redshaw, V. C. Gibson, A. J. P. White, D. J. Williams and M. Elsegood, Chem. Eur. J., 2000, 6, 221, and in G. J. Britovsek, B. Dorer, V. C. Gibson, B. S. Kimberley and G. A. Solan, WO9912981, 1999 (BP Chemicals Ltd.).
Hence new oligomerization catalysts are of great interest in the industry because they offer many new opportunities for providing new processes and products in a cheaper and more efficient manner. The following invention relates to new oligomerization technology based upon new late transition metal catalyst compounds.